There are well known in the art the cold start problems in the internal combustion engine of a vehicle in days in which the temperature is lower than 18 degrees Celsius, when the engine is supplied with a fuel mixture containing more than 85% ethanol and less than 15% gasoline.
The ethanol and the methanol, for example, present a high flash point and, for such reason, these fuels or mixtures containing a substantial percentage of these fuels, when below a certain temperature, do not spray adequately, impairing or even preventing its explosion inside the combustion chamber. This phenomenon, known as “cold start problem”, is faced by vehicle users using ethanol or methanol, upon the cold start of the engine in cold days, usually in an ambient temperature lower than 18° C.
In order to overcome said cold start problem of the vehicle engine, there were provided solutions which, inject a small amount of gasoline in the combustion. Since the gasoline is more volatile than the ethanol and the methanol, it causes the lowering of the flash point of the fuel mixture to be burned in the combustion chamber, thereby allowing the engine to start.
However, the technique of injecting gasoline during the engine start causes a high level of emission of pollutants.
A system developed more recently in the market comprises the use of a heater to preheat the fuel for a few seconds before the engine start, in order that, upon the request of a start, the fuel to be injected is already in a temperature hot enough to be suitably sprayed in the combustion chamber, thus allowing a satisfactory start of the vehicle engine, without the need of the extra gasoline injection. This system represents a more sophisticated technique which may reduce the level of pollutants produced during the vehicle start.
A major challenge of using the preheating system is due to the need for developing highly efficient heaters, otherwise the high electrical energy demanded by the cold start heaters may cause the discharge of the vehicle battery after a few successive starts. It should be observed that, during the engine start, it is already required a huge energy peak for feeding the starter motor, even without the cold start heaters.
Thus, the technical solutions presented so far only target the solution of the “cold start problem”.
However, the “cold start problem” is just one of the many problems regarding efficiency and emission of pollutants caused by the burning of the cold or not heated fuel. Besides the cold start problems in low temperature environments when using a fuel of high flash point, there is an additional problem, caused by the natural difficulty of burning any fuel, when the latter is at a temperature interiorly distant from that of its flash point, or commonly named “cold fuel”.
It should also be pointed out that the vaporization point of a liquid depends on the pressure in which, the latter is found. The typical pressure inside a fuel line in 1.0 liter vehicles of indirect injection is around 4.2 bar, a condition in which the vaporization temperature of the fuel is higher than the vaporization temperature when the fuel is under atmospheric pressure. For vehicles having direct fuel injection these values (pressure and vaporization temperature) are further increased.
The increase in temperature of the fuel is just one means for achieving a fuel spray formed by micrometric pulverized droplets, which will burn more easily when in contact with the spark from the ignition coil in the combustion chamber or when the fuel is compressed therein to a certain pressure (diesel fuel).
Theoretically, an engine running in a steady state would be hot enough to keep running, even if the fuel injected in the combust ion chamber is somewhat “cold”, for there is some amount of thermal exchange between the heat dissipated by the engine (or combustion chamber) and the fuel, for a brief moment. However, this is not a working condition which presents an optimized thermo-energetic efficiency.
It is not rare to detect engine faults, jolts, engine slow response after pressing the gas pedal or even high emission of pollutants due to a deficient fuel burning. In “flex vehicles” (driven by ethanol and/or gasoline in any mixture proportion) it is known that the engine yield is not optimized, since it is an engine which has to function reasonably well with both types of fuel, however it is not the ideal engine to run only on gasoline or only on ethanol. An effective heating system, having thermal management of the fuel, tends to provide optimized conditions when raising the fuel (for example, ethanol or gasoline) to better burning conditions (by heating the fuel to temperatures closer to the vaporization point thereof) and to a consequent better yield of the engine.
A heating system having thermal management of fuel to be maintained operating during the entire time the engine is running would be an effective solution to achieve high performance (energetic optimization) of the engine, better vehicle handling, with fast responses when pressing the accelerator pedal, with optimized torque and power and lower pollutant emissions not only in “flex” type vehicles (two or three fuels), but also in vehicles provided with an internal combustion engine running on just one fuel, liquid or gas.
The radiator of a vehicle is a heat exchanger whose goal is to cool the engine (or protection against over-heating). For exchanging the heat of the engine and the components thereof to the radiator, water is used as the intermediate (circulating) fluid, acting like a “heat carrier” between the engine and the radiator.
Presently, the heat transmitted to the radiator water is lost, even unwanted energy, since if this heat is stored in the water the latter loses its efficiency as a thermal exchange fluid. The colder the radiator water, the more heat amount it will be able to absorb from the engine in a shorter period of time.
Another thermal exchange point which is essential for the proper operation of the vehicle engine is the one that occurs between the lubricant oil and the engine parts, the oil having two vitally important functions: lubrication and cooling of the engine components, in which in some parts such as the crankshaft, bearings, camshaft, rods and pistons, the cooling is only carried out by the engine oil.
The oil, when overheated, loses viscosity and is more exposed to deterioration, and therefore loses its lubrication properties, which may cause from poor operation of the engine components to major damages or even destruction of the vehicle engine. Nowadays, some vehicles present an oil cooler. It comprises a heat exchanger, usually of the plate type, located between the engine block and the oil filter, or being part of the oil module itself (in this case, more commonly found in heavy vehicles), functioning as a heat exchange enhancer between the lubricant oil and the radiator. However, oil coolers presently used do not exchange heat with the fuel.
Thus, it is highly desirable to provide a system which is able to use the thermal energy generated by the engine such as, for example, by the cooling of the cooling fluids (oil and water) of the vehicle engine or by the combustion gases and simultaneously to heat the fuel to temperatures closer to the vaporization point. This would be advantageous in order to optimize the energetic efficiency in the engine cooling, besides improving the level of emission of pollutants due to the better burning of the heated fuel.